Army Res. Reactor

US Army Materials Technology Laboratory


       The first nuclear research reactor designed to meet the needs of the research programs on material for the U.S. Army Ordinance Corps. was constructed at Watertown. Massachusetts, during the late 1950s and 1960.  The reactor was dedicated in May 17, 1960, to the memory of the late Dr. Horace Hardy Lester, who won national recognition as a pioneer in the field of industrial radiography. 
   Initial criticality of the nuclear reactor was achieved on June 15, 1960, at a power level of 1 MW.  Post-neutron tests consisted of shim rod calibration, power calibration, temperature and void coefficients of reactivity measurements, and determinations of the worth of experimental facilities were conducted, culminating on September 16, 1960.    
    Various solid-state physics research programs and experiments were conducted at the 1 MW level through June 1966 by the Army Materials and Mechanics Research Center (AMMRC, now AMTL).  The reactor was also used extensive by the U.S. Army Picatinny Arsenal for study of explosive-type materials.  Other U.S. Army users included the Detroit and Frankford Arsenals, and the Natic and Electronics Research and Development Laboratories.  Some of the programs conducted by the reactor users included:  experiments in the structure of heavy-metal azides, lattice dynamics studies on explosive-type materials and determinations of bibrational spectra of organic secondary explosives. 
    The reactor license was amended in June 1966 to allow the power level to be inc to 2 MW to provide higher neutron fluxes for exp.  The approach to 2 MW began on June 6, 1966 , and was completed on June 15.  The procedure that was followed was to increase power in steps of 200 KW and observe all measured parameters for several hours at each step.    
    The reactor's license was updated in 1969 from 2 MW to 5 MW.  On August 22, 1969, the power-escalation program began and the reactor power was increased in 1 MW steps to the maximum licensed power of 5 MW.  THis program was completed with a 79-hour 5 MW run during the week of September 8 with no abnormal results observed during the power-escalation program.
    In December, 1969, the Department of the Army decided to shut down the operation of the AMTL reactor and to place the facility in a standby condition in 1972.  On March 27,1970 the reactor operations were shut down and the reactor was placed in standby mode.  A deactivation report was submitted to the Division of LIcensing and to the Army Reactor Systems HEalth and Safety Review Committee in December, 1970.  


Site History:

The U.S. Army Materials Technology Laboratory (MTL), commonly known as the Watertown Arsenal, occupies 47.5 acres on Arsenal Street in Watertown, Massachusetts. MTL is located on the north bank of the Charles River and encompasses 36.5 acres approximately 5 miles west of Boston. Eleven acres of inactive MTL land situated between North Beacon Street and the Charles River was leased to the Commonwealth of Massachusetts in 1920 and currently contains the North Beacon Street Park and the Watertown Yacht Club.

The facility was originally established as the Watertown Arsenal in 1816. The facility continued to expand and occupied 131 acres and employed 10,000 people at the end of World War II. The site was used for small arms maintenance and ordnance supplies; ammunition and pyrotechnics production; paint, lubricant, and cartridge testing and experimentation; manufacture of guns and cartridges; and development of advanced metallurgical processes used in the casting, welding, and machining of artillery pieces. A research nuclear reactor was used for molecular and atomic structure research activities from 1960 to 1970. Although the reactor was deactivated in 1970, it is currently being decommissioned under the jurisdiction of the Nuclear Regulatory Commission. In 1968, approximately 55 acres were sold to the Town of Watertown. Of the 47.5 acres retained by the Army, 36.5 acres became the Army Materials and Mechanical Research Center (AMMRC). In 1985, AMMRC became MTL. The current mission of MTL includes testing material; developing weapons, ammunition, and lightweight armor; and manufacturing testing technology.

In October 1988, Congress recommended the closure of the facility. The U.S. Army Toxic and Hazardous Materials Agency (THAMA) had already initiated the first stage of the closure plan, the preliminary assessment/site inspection, which was conducted in 1987. The Army also conducted a soil, sediment, and ground water sampling program in 1988, from which a remedial investigation (RI) report was produced. The data obtained from this sampling could not be verified or validated by the Army. Subsequently, the Army completed a Draft Phase 1 Remedial Investigation Report in April 1991 and a Phase 2 report in October 1992.

Sampling during these investigations indicated contamination of ground water, soil, surface water, and sediments at MTL. Contaminants detected above background concentrations at the site include volatile and semi-volatile organic compounds, PCBs, pesticides, inorganic elements, and radioactive substances. PCBs were detected on the property on the surface of electrical transformers and in the surrounding soil. Samples collected from on site storm drains indicate the presence of several organic compounds and inorganic contaminants related to site activities. However, there are other potential sources of contamination from nearby industrial activity.

The only known drinking water well within 4 miles of the site not separated by the Northern Boundary Fault, is a private well 2.5 miles northwest of the property. Municipal drinking water within 4 miles of the site is supplied by surface water sources located to the west of MTL, and are unaffected by the site. The Charles River is used for recreational boating, swimming, and fishing.

The active portion of MTL is completely fenced and public access is restricted 24-hours by a guarded gate. Eight people occupy housing located on the property. Approximately 600 people are currently employed at MTL.





Control room.

Reactor containment.

Site Plan.

Area map.

Reactor Floor Plan.

Cutaway view of the containment.

Reactor core.


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